Pre-heating apparatus in rotary kiln plant

ABSTRACT

Pre-heating Apparatus for pre-heating pulverous raw material (e.g. cement raw meal) prior to its introduction into a rotary kiln for burning is disclosed. In construction the pre-heating apparatus includes four strings of treating units, each unit including separation and heat exchange zones, wherein the units of each string are disposed in series superimposed relationship in communication with the kiln and wherein the four strings are arranged symmetrically with respect to determined planes oriented with respect to the kiln axis and kiln outlet.

nit ts l Tet [1 1 Engel Sept. 17, 11974 [5 lPRE-HIEATTNG APPARATUS lINROTARY 3,207,494 9/1965 lager 432/58 KHLN PLANT 3,653,644 4/l972Polysius et alm. 34/57 3,656,722 4/1972 Polysius et al. 34/57 RInventor: Erland Uhrlswffer s 3,664,650 5/1972 Weber er al. 432/117Copenhagen-Valby, Denmark [73] Assignee: F. L. Smidtli & (30.,Cresskill, NJ. Primary ExaminerJ0hn J. Camby I Assistant Examiner-HenryC. Yuen [22] Filed 1972 Attorney, Agent, or Firm-Pennie & Edmonds [21]Appl. No.: 310,999

57 ABSTRACT [30] Foreign Application Priority Data l 1 Dec 2 1971 GreatBritain 56051, Pre-heatmg Apparatus for pre-hea'ting pulverous rawmaterial (e.g. cement raw meal) prior to its introduc- U S tlOn into arotary for burning is diSClOSd. In con- 34/57 struction the pre-heatingapparatus includes four [51] Km Cl FT") 15/00 strings of treating units,each unit including separation [58] i 105 117 and heat exchange zones,wherein the units of each 432/129 34/57 k string are disposed in seriessuperimposed relationship in communication with the kiln and wherein thefour strings are arranged symmetrically with respect to de- [56]References Cited termined planes oriented with respect to the kiln axisand kiln outlet. UNITED STATES PATENTS 2,785,886 3/1957 Miiler 432/16 6Claims, 4 Drawing Figures PAIENIEB SEPI 1:914

SHEET 3 OF 3 FIG.

FIG.

T RE-HEATING APPARATUS IN ROTARY lKlllLN PLANT BACKGROUND OF THEINVENTION This invention relates generally to apparatus for preheatingpulverous material, such as cement raw meal, prior to its introductioninto a rotary kiln for burning. More particularly this invention relatesto pre-heating apparatus of the type which includes at least one stringof series connected treating units in each of which preheating isaccomplished by heat exchange between the pulverous material and thesmoke gases from the kiln. Each treating unit of this type ofpre-heating apparatus commonly includes a riser pipe through which smokegas from the kiln flows and into which the pulverous material isintroduced. This riser pipe defines a chamber in which heat exchangebetween the gas and pulverous material takes place. Such treating unitsalso commonly include a separator, such as a single or twin cycloneseparator, in which the pulverous material is separated from the kilnsmoke gases after the heat exchange has occurred.

In a plant utilizing this kind of pre-heating apparatus, as for example,those commonly found in the cement industry, the hot gases from therotary kiln are drawn by means of a fan successively through theindividual treating units which are arranged in superimposed steps orstages. As far as the lowermost stage is concerned, i.e., the stagefirst passed by the smoke gases from the rotary kiln, the cyclone outletpipe in that stage is commonly passed directly to the rotary kiln. Inother stages of the apparatus, the outlet pipes of the respectivecyclone separators commonly open into the riser pipe leading to thecyclone separator of the preceeding stage in the direction of flow ofthe smoke gases. Each riser pipe is provided with means for feeding itwith the cement raw meal which, on its way through the treating unitslocated at the various stages, is successively brought into contact withhotter and hotter smoke gas and is thereby heated to a high temperature.In each individual stage therefore the pulverous raw material issubjected to a separate pre-heating treatment.

In known plants utilizing the above described type of pre-heatingapparatus, effective pre-heating of the raw meal (sometimes followed bya partial calcination or expulsion of CO is carried out, it will berecognized, in such a manner that the heat content of the fuel fed tothe rotary kiln is utilized in an economically advantageous manner.

The early pre-heating apparatus of this kind generally consisted of buta single string of treating units. The modern day tendency in the cementindustry and in other industries is, however, to use continually largercapacity plants and larger rotary kilns, which means that the capacityof the corresponding raw meal preheaters must likewise be increased. Oneknown way to meet this requirement for increased capacity is to providethe kiln with two parallel strings of treating units of the typedescribed. This invention meets the requirement for increased capacityby providing a specially constructed pre-heating apparatus which hasseveral other advantages over known pre-heaters of the type described.

SUMMARY OF THE INVENTION In accordance with the present invention apreheating apparatus having four strings of treating units arrangedsymmetrically both with respect to a vertical plane through the kilnaxis and with respect to another vertical plane, perpendicular to theformer adjacent to or in front of the smoke gas outlet of the kiln isprovided. Structurally, a pre-heating apparatus according to thisinvention is very compact, provides a very suitable riser pipearrangement and lends itself to low material consumption for building upthe necessary supporting structures.

Furthermore, a pre-heating apparatus constructed according to thisinvention ensures that the flow paths for the pulverous material and forthe smoke gases are the same in each string, both media being equallydistributed to the four strings. Moreover, the presence of the fourstrings affords a high degree of reliability for the total kiln plant,because in the case of failure or inspection of one or more strings, itis possible to continue operation with reduced production by workingwith a reduced number of strings without stopping the kiln.

Preferably each string includes four treating units and the four riserpipes belonging to the lowermost units preferably unite into a commonshaft or conduit into which the rotary kiln opens. To achieve this, the

four riser pipes may advantageously unite in pairs into two commonintermediate riser pipes, and the two common riser pipes thus producedmay unite downwards into the common conduit.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of apre-heating apparatus constructed according to this invention.

FIG. 2 is a side elevation view of the pre-heating apparatus shown inFIG. ll;

FIG. 3 is a cross-sectional view taken along the line 3-3 of FIG. 2; and

FIG. 4 is a cross-sectional view taken along the line 4l-4l of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION With reference to FIG. I, thepre-heating apparatus shown includes four strings each of which includesfour treating units which are disposed in series communicatingrelationship with respect to each other. As will become apparent as thedescription proceeds the treating units of each string are also disposedin superimposed relationship with respect to each other and eachtreating unit includes basically a riser pipe defining a heat exchangechamber and a communicating single or twin cyclone separator. Pulverousmaterial, such as cement raw meal, is thus subjected to four stages orsteps of treatment as it passes through the riser pipe and cycloneseparator of each treating unit in a given string. The treating stagesto which the pulverous material is subjected in each string are countedin the direction of transport of material to the kiln. Thus the firststage is uppermost, i.e., it is located most remotely to the kiln. Inthe Figures the relationship of the individual components of thepre-heating apparatus to the individual stages or steps of treatment isindicated by the addition of a letter index following the particularreference numeral used. Thus, the four stages of treatment are denotedby the letters A to D, commencing from above.

Located at the first stage are four twin cyclones IA, 2A, 3A and 4A withcorresponding communicating riser pipes 5A, 6A, 7A and 8A. These riserpipes lead from the top of four single cyclones 9B, 108, MB and 1213 inthe second stage which also includes corresponding communicating riserpipes 13B, MB, 153 and 1613 leading, in turn, from the tops of foursingle cyclones 17C, l8C, 19C and 20C in the third stage. To thecyclones in the third stage belong communicating riser pipes 21C, 22C,23C and 24C leading, in turn, from the top of two twin cyclones 25D and26D in the fourth stage. The treating units in the fourth stage alsoincludes riser pipes 27D and 28D each of which includes two branches27', 28 which, in turn, lead into one section of one of the twincyclones 25D, 26D of the treating unit in the fourth stage. As shownbest in FIG. 2 riser pipes 27D, 28D lead directly into a common shaft 29opening into the rotary kiln 20.

As will be best seen in FIGS. 3 and 4, the four strings of thepre-heating apparatus are arranged symmetrically both with respect to avertical plane through the kiln axis and with respect to anothervertical plane at right angles to the former located in front of oradjacent to the smoke gas outlet of the kiln.

In normal operation the hot gases from the rotary kiln 30 are drawn, bymeans of a fan (not shown), successively through the individual treatingstages of the apparatus in equal quantities through the individualstrings. Thus, one quarter of the smoke gas proceeds along the path fromthe rotary kiln 30 defined by shaft 29, riser pipe 27D, one of the twincyclones 25D, riser pipe 211C, cyclone 37C, riser pipe 138, cyclone 9B,riser pipe 5A and both twin cyclones 1A at which point the smoke gas isremoved by suction through the central outlets 1' via a pipe system (notshown). In analogous manner one-quarter of the smoke gas from the kilnpasses through each of the remaining strings in the pre-heater. The flowpaths through the four strings are of equal and uniform length, and thecross-sectional area along the four flow paths varies equally. Thus thegas flow advantageously is distributed exactly equally to the four flowpaths defined by the four strings.

The pulverous raw meal is fed to the individual strings at the uppermosttreating stage through feed pipes 31, 32, 33 and 34. The raw meal thenpasses, via gate valves 35, 36, 37 and 38 which act to prevent the smokegases from entering the feed pipes while permitting passage of the rawmeal, into the riser pipes 5A, 6A, 7A and 8A. In its further conveyancethe raw meal flows suspended in the smoke gases through the riser pipes5A, 6A, 7A and 8A. During passage through these riser pipes, heatexchange between the raw meal and the gas occurs heating the raw mealand cooling the smoke gas. From the first stage riser pipes 5A, 6A, 7Aand 8A the smoke gases and the raw meal suspended therein pass into thetwin cyclones 1A, 2A, 3A and 4A in the first treating stage. In thesecyclones, and in the cyclones at other treating stages, centrifugalforce and gravity cooperate in a conventional manner to separate smokegas and raw meal from each other.

The raw meal leaves the first stage cyclones through raw meal outletpipes 39, 40, 41 and 42 via built-in gate valves 43, 44, 45 and 46 whichact to prevent the smoke gases from moving rearward through outlet pipes39, 40, 41 and42 into the cyclones EA, 2A, 3A and 4A, but to permitpassage of raw meal into the second stage riser pipes 138, MB, 15B and168 where renewed heat exchange takes place in the same manner as in thefirst stage riser pipes.

From the second stage riser pipes the raw pulverous material passes intothe second stage cyclones 98, 10B, 11B and 128 where smoke gas and rawmeal are again separated in the same manner as in the first stagecyclones. From the second stage cyclones the raw material passes throughraw meal outlet pipes 47, 48, 49 and 50 via gate valves 51, 52, 53 and54 where the raw meal is fed into the third stage riser pipes 21C, 22C,23C and 24C for further heat exchange with still hotter gases. In thethird stage cyclones 17C, 18C, 19C and 20C gases and raw meal are againseparated as in the first and second stage cyclones. The separated rawmeal then passes through raw meal outlet pipes 55, 56, 57 and 58 viagate valves 59, 60, 61 and 62 into the shaft or conduit 29, from whichthe raw meal, suspended in heat exchange relationship with the smokegases passes through the fourth stage riser pipes 27D and 28D forfurther heating by ever hotter gases and into the twin cyclones 25D and26D of the fourth treating stage for separation. From the fourth stagecyclones separated raw meal passes through raw meal outlet pipes 63, 64,65 and 66 which unite, in pairs, into intermediate outlet pipes 67 and68 which, in turn, lead directly into shaft 29.

The inlet pipes 311, 32, 33, and 34 for introducing raw meal into thefirst stage riser pipes are provided with distributing devices (notshown) which serve to aid uniform mixing of the raw meal in the smokegas flow.

With a pre-heater constructed according to this invention, the raw mealon its way through the individual cyclones and, more particularly,through their respective riser pipes, is brought successively intointimate contact with smoke gas of continually higher temperature and isthereby ultimately brought up to a high final temperature. The uniformlydistributed pipe connections 55, 56, 57 and 58 to the shaft 29 ensure afavorable, uniform distribution of the pre-heated raw meal which isintroduced into the fourth stage twin cyclones 25D and 26D. Theintermediate outlet pipes 67 and 68 likewise open symmetrically into theshaft 29 within which they continue as channels serving to feed the rawmeal into the rotary kiln 30.

Similarly to the smoke gases the raw meal flows along four identicalpaths, and, provided that the amount of raw meal fed to the rotary kiln30 is distributed equally per unit of time between the four feed pipes31, 32, 33 and 34, the quantity and temperature of the meal delivered tothe kiln from each string will be the same.

I claim:

1. Apparatus for pre-heating pulverous raw material used for producingcement or the like in a rotary kiln having a gas outlet end comprising:

a. four strings of raw meal treating units, each including a heatexchange zone in which the pulverous material and kiln smoke gases arebrought into heat exchange relationship, and a separation zone in whichthe pulverous material entrained in a smoke gas stream from the kiln isseparated from the gas, each string separately communicating with asingle through-going substantially vertical smoke gas conduit connectedto the gas outlet end of the kiln such that they are disposedindependently of the three other strings in a manner which permitsindependent operation of one or more strings when one or more strings isentirely inoperable from the outlet of the kiln, each string including aplurality of said treating units arranged in series superimposedcommunicating relationship with respect to each other with said stringsbeing interconnected at the lower portions by material outlet pipes tosaid single through-going conduit, said strings being arrangedsubstantially vertically and symetrically with respect to a first planeextending vertically through the kiln axis and with respect to a secondplane disposed in perpendicular relationship to said first planeadjacent the kiln outlet such that the gas flow and the raw materialflow in each string is along independent and substantially similarpaths;

. supply means for delivering the pulverous material into each stringvia the treating unit thereof most remotely located relative to the kilnoutlet; and

. means for moving the hot kiln gases through the 2. Apparatus accordingto claim ll wherein each string includes four of said treating units.

3. Apparatus according to claim 1 wherein the treating units of eachstring located nearest the kiln are disposed in communicatingrelationship with respect to the single substantially vertical conduitwhich is disposed in direct communicating relationship to the kiln.

4. Apparatus according to claim. 3 wherein the treating units of eachstring located nearest the kiln communicate in pairs with anintermediate conduit which is disposed in communicating relationshipwith respect to said common conduit.

5. Apparatus according to claim 4 wherein each string of treating unitscomprises four stages of left and right cyclones in staggeredrelationship to one another.

6. Apparatus according to claim 5 wherein the upper treating unit ofeach string includes a twin cyclone separator.

1. Apparatus for pre-heating pulverous raw material used for producingcement or the like in a rotary kiln having a gas outlet end comprising:a. four strings of raw meal treating units, each including a heatexchange zone in which the pulverous material and kiln smoke gases arebrought into heat exchange relationship, and a separation zone in whichthe pulverous material entrained in a smoke gas stream from the kiln isseparated from the gas, each string separately communicating with asingle through-going substantially vertical smoke gas conduit connectedto the gas outlet end of the kiln such that they are disposedindependently of the three other strings in a manner which permitsindependent operation of one or more strings when one or more strings isentirely inoperable from the outlet of the kiln, each string including aplurality of said treating units arranged in series superimposedcommunicating relationship with respect to each other with said stringsbeing interconnected at the lower portions by material outlet pipes tosaid single through-going conduit, said strings being arrangedsubstantially vertically and symetrically with respect to a first planeextending vertically through the kiln axis and with respect to a secondplane disposed in perpendicular relationship to said first planeadjacent the kiln outlet such that the gas flow and the raw materialflow in each string is along independent and substantially similarpaths; b. supply means for delivering the pulverous material into eachstring via the treating unit thereof most remotely located relative tothe kiln outlet; and c. means for moving the hot kiln gases through thetreating units of each string in a direction countercurrent to thedirection of flow of pulverous material therethrough.
 2. Apparatusaccording to claim 1 wherein each string includes four of said treatingunits.
 3. Apparatus according to claim 1 wherein the treating units ofeach string located nearest the kiln are disposed in communicatingrelationship with respect to the single substantially vertical conduitwhich is disposEd in direct communicating relationship to the kiln. 4.Apparatus according to claim 3 wherein the treating units of each stringlocated nearest the kiln communicate in pairs with an intermediateconduit which is disposed in communicating relationship with respect tosaid common conduit.
 5. Apparatus according to claim 4 wherein eachstring of treating units comprises four stages of left and rightcyclones in staggered relationship to one another.
 6. Apparatusaccording to claim 5 wherein the upper treating unit of each stringincludes a twin cyclone separator.